Numerous materials which are available for manufacturing electro technical products differ in contexture and origin: basic chemical elements, chemical compounds, alloys, artificial compounds and complex materials. High purity soft copper and compressible aluminium are mostly used materials in electro technical compounds. Good properties of aluminium and its alloys as a conductible material are: high electrical and thermal conductivity, small specific mass, good technological and mechanical properties, chemical stability and resistance to arc discharge. Copper has the best electrical and thermal conductivity. Electrical conductivity depends on the percentage of admixtures and impurities as well as the rate of plastic deformation and recrystallization during the process of manufacturing. The feature of high conductive compound alloys like aluminium and copper is the possibility of galvanic cells formation. Therefore, the merging aluminium and copper by usual welding methods is not allowed due to electrochemical corrosion which causes the deterioration of aluminium as an anode in galvanic cell and humid conditions. The Cu/Al joint usage in power lines is tested in this paper. Product makes a compound of soft copper alloy Cu-ETP (CW004A) and compressible aluminium alloy EN AW-1050A. For merging of the aforementioned, friction welding (FRW) method was used. The aim of this research was to determine microstructural properties of copper and aluminium alloys and their joint, and to correlate them with the effect of simulated techno chemical conditions in the ambient of artificial rain and 3,5% NaCl solution.